1. Field of the Invention
The present invention relates to a flat display device which is characterized in a wiring (pattern) for connecting an electrode and a driver circuit, and a wiring method for connecting the electrode and the driver circuit of the flat display device. Further, the present invention relates to an image display system which is constructed in a manner that a plurality of display panels comprising a flat display device are arranged in an adjacent state.
2. Description of the Related Art
As one kind of a flat display panel type display, there is an electro-luminescent display (hereinafter, referred simply to as xe2x80x9cELDxe2x80x9d). The ELD has been made based on the principle of an electro-luminescence which is a light emission phenomenon taken place when a voltage is applied to a fluorescent substance (material). Further, the ELD has the following various merits (1) to (3):
(1) since the ELD is a self light emission type display, it has a high luminance (thus, high contrast), a wide viewing angle, and a high response speed;
(2) since the whole of display device consists of a solid, the display device is strong in vibration; and
(3) it is possible to readily make the ELD thin.
In the light of a chemical composition of display material (fluorescent material), the display device of the ELD is classified into an inorganic EL using an inorganic compound and an organic EL using an organic compound. Further, in the light of a physical shape of the display material, the display device of the ELD is classified into a dispersed type EL using a powdered display material, and a thin film EL using a dense thin film display material. In recent years, among these ELs, in particular, an organic thin film EL has attracted special interest from the following reasons. More specifically, a high luminance is obtain at a low voltage, and a fluorescent color itself of the organic compound is a light emission color; therefore, selection of the light emission color is easy.
FIG. 13 shows one example of a structure of the organic thin film EL. In this organic thin film EL 50, an anode electrode 52 is formed like a stripe on a glass substrate 51, and has a film thickness of about several hundreds of angstrom to several xcexcm. The anode electrode 52 is, for example, a transparent electrode consisting of ITO (indium-tin oxide), and is also called as a column electrode because an direction of the stripe is a longitudinal direction of a display screen.
The column electrode 52 is formed with an organic layer 53 having a film thickness of about several hundreds of angstrom to several xcexcm, at its upper portion and surrounding. The organic layer 53 has a three-layer structure in which an organic positive hole transport layer 54, an organic light emission layer 55 and an organic electron transport layer 56 are laminated in order when viewing from the column electrode 52 side.
The organic positive hole transport layer 54 consists of a mixture of Alq3 (tris-(8-hydroxyquinoline) aluminum) and DCM (4-dicyanomethylene-6-(p-dimethyleaminostyril)-2-methyle-4H-pyrane, for example. Further, the organic positive hole transport layer 54 has a function of moving a positive hole injected from the column electrode 52 to the organic light emission layer 55. The organic electron transport layer 56 consists of a triphenyldiamine derivative (TPD) (N,Nxe2x80x2-bis (3-methyl phenyl) 1,1xe2x80x2-biphenyl-4,4xe2x80x2-diamine). Further, the organic electron transport layer 55 has a function of moving an electron injected from a row electrode 57 which will be described later to the organic light emission layer 55.
The organic light emission layer 55 consists of a fluorescent material corresponding to a color to be displayed; for example, DCM is used as a red fluorescent material, Alq3 is used as a green fluorescent material, and a zinc complex of Zn(oxz) 2 (2-(o-hydroxyphenyl)-benzoxazole is used as a blue fluorescent material. In the case of displaying a white color, the following methods are employed; more specifically, there are the methods of dispersing red, green and blue fluorescent materials in a high molecule so as to be synthesized and laminating these fluorescent materials so as to be synthesized.
A cathode electrode 57 is formed like a stripe so as to be perpendicular to the column electrode 52 on the organic electron transport layer 56. The cathode electrode 57 consists of a metal such as aluminum and an alloy of aluminum and lithium, for example, and is also called as a row electrode because the direction of the stripe is a lateral direction of the display screen.
When a voltage is applied between the column electrode 52 and the row electrode 57, a positive hole injected from the column electrode 52 is moved to the organic light emission layer 55 via the organic positive hole transport layer 54 while an electron injected from the row electrode 57 being moved to the organic light emission layer 55 via the organic electron transport layer 56. The positive hole and the electron are mutually recombined at the intersecting point of the column electrode 52 and the row electrode 57 in the organic light emission layer 55. The fluorescent material constituting the organic light emission layer 55 regards the recombination as an external stimulus, and then, is excited. When returning from the excitation state to a ground state, the fluorescent material radiates a fluorescence; therefore, a light is observed from the glass substrate 51 side.
Thus, the column electrode 52 and the row electrode 57 are used as a signal electrode and a scanning electrode, respectively, and then, a display signal and a scanning signal are supplied to a display panel using the organic thin film EL as a display device, and thereby, it is possible to display a desired image using each intersecting point of the column electrode 52 and the row electrode 57 as a pixel.
FIG. 14 is a circuit diagram showing a construction of a display unit for displaying an image on a display panel 100 using the organic thin film EL as a display device. An analog video signal (display signal) supplied from a video signal reproduction system (not shown) is converted into a digital signal by means of an A/D converter 101, and thereafter, is supplied to a column driver (driving circuit for display signal supply) 102. The column driver 102 stores the display signal thus supplied by one line of a screen, and then, supplies the display signal thus stored to all column electrodes (not shown) of the display panel 100 in parallel.
On the other hand, a row driver (driving circuit for scanning signal supply) 103 successively scans the row electrode (not shown) of the display panel 100 one by one at intervals of one field (or one frame). Each operation of the A/D converter 101, the column driver 102 and the row driver 103 is controlled by means of a controller (e.g., CPU) 104, and a power supply voltage is supplied from a power supply block 105 to these A/D converter 101, column driver 102, row driver 103 and controller 104.
Conventionally, in the display unit, in order to connect the column electrode and the row electrode to a driver circuit (the column driver 102 and the row driver 103 shown in FIG. 14, respectively), a wiring has been given so that these electrodes and the driver circuit are connected at an edge portion of each electrode (i.e., near by the organic thin film EL) in an outer side of a sealing cap for covering and protecting a back side (i.e., side opposite to the glass substrate) of the organic thin film EL. As a result, in the conventional organic thin film EL, the wiring for connecting the column electrode and the row electrode with the driver circuit has been arranged like a picture frame, that is, around the edge of the organic thin film EL.
FIG. 15 shows one example of a state that the aforesaid wiring is given to the organic thin film EL so as to be connected with the driver circuit. The back side of the organic thin film EL 50 shown in FIG. 13 is covered with a sealing cap 110 (the downward portion of FIG. 15 is shown as a cross section) in an outer side of the cap 110. The edge portion of the column electrode 52 and a column driver substrate 112 mounted with a column driver IC 111 are connected by a flexible printed cable (FPC) substrate 113. Likewise, the edge portion of the row electrode 57 and a row driver substrate 115 mounted with a row driver IC (driver circuit for scanning signal supply) 114 are connected by an FPC substrate 116. As a result, The FPC substrates 113 and 116 are arranged around the edge portion of the organic thin film EL 50.
Moreover, in the example shown in FIG. 15, in addition to these EPC substrates 113 and 116, the column driver substrate 112 and the row driver substrate 115 are also arranged around the edge portion of the organic thin film EL 50 like a picture frame. In this case, these FPC substrates 113 and 116 are bent upwardly, and thereby, it is possible to make an arrangement such that the column driver substrate 112 and the row driver substrate 115 are not arranged around the edge portion of the organic thin film EL 50. However, even if the aforesaid arrangement is made, after all, the FPC substrates 113 and 116, or at least their part is arranged around the edge portion of the organic thin film EL 50.
By the way, in recent years, the flat display panel type display has a tendency to have a large-size screen. However, the following problems arise. More specifically, in general, when a display panel becomes a large size, a resistance of electrode increases; for this reason, a driving voltage must be made high. Moreover, in particular, in the case of the organic thin film EL, a current proportion to a pixel size must be supplied to each pixel; for this reason, a power consumption increase accompanying with the large-size screen.
So, in the case of the organic thin film EL, in place of making large individual display panel and pixel, as shown in FIG. 16, a plurality of display panels 100 are arranged like a tile, and then, these display panels 100 are used as a single screen. This is an effective method for making large a screen while restricting an increase of power consumption.
In the conventional organic thin film EL, as described above, the wiring for connecting the column electrode and the row electrode with the driver circuit is arranged around the edge portion of the organic thin film EL. For this reason, in the case where a plurality of display panels are arranged like a tile, as also shown in FIG. 16, a wiring 120 (equivalent to the FPC113 and 116 in the example of FIG. 15) becomes a state of being interposed between adjacent display panels 100. As a result, in the case where these display panels are used as a single screen so as to display an image, a non-display area by the wiring exists for each space between adjacent display panels, and becomes conspicuous; for this reason, the display panel as described above is not adaptable to a practical use.
Moreover, in general, as a factor of lowering a reliability of integrated circuit, there is the following phenomenon. More specifically, a wiring of the integrated circuit increases a resistance and makes a breakdown by a migration (i.e., phenomenon such that when a density of a current flowing through a wiring metal becomes high, a metal ion is moved by a momentum exchange of an electron and a metal ion). It has been known that the higher a surrounding humidity is, the easier this migration takes place.
Thus, in the conventional organic thin film EL, as described above, the wiring for connecting the column electrode and the row electrode with the driver circuit is performed at the outside of the sealing cap; for this reason, the wiring is in a state of contacting with an external air. As a result, in the case where a display is used at a place having a high humidity, the migration by the wiring is easy to take place; for this reason, this causes a problem of lowering a reliability of the display.
It is, therefore, an object of the present invention to provide an organic thin film EL which has a wiring capable of reducing a non-display area in the case of using a plurality of display panels as a single screen, and preventing a generation of migration. Further, another object of the present invention is to provide a method of forming this wiring to the organic thin film EL. Furthermore, another object of the present invention is to provide an image display system using the aforesaid display panel.
To achieve the above objects, the present invention provides a flat display device laminating a display material and an electrode, wherein a wiring for connecting the driver circuit to the electrode is led from an inside of a sealing member covering a back side of the flat display device to the back side of the flat display device.
Further, the present invention provides a flat display device laminating a display material and an electrode, wherein a driver circuit connected to the electrode is arranged inside the sealing member covering a back side of the flat display device, and a wiring for connecting a power supply circuit and a signal supply circuit to the driver circuit is led from the inside of the sealing member to the back side of the flat display device.
Further, the present invention provides a wiring method for connecting an electrode to a driver circuit in a flat display device laminating a display material and an electrode, comprising the following steps of: forming an insulative protection layer on a back side of the flat display device; mounting a connector for connecting a driver circuit to the electrode on the protection layer, and forming an wiring for connecting the connector to the electrode on the protection layer; covering the back side of the flat display device with a sealing member having an opening at its part thereof so that the connector is passed through the opening; and sealing a contact portion of the connector with the sealing member.
Further, the present invention provides a wiring method for connecting an electrode to a driver circuit in a flat display device laminating a display material and an electrode, comprising the following steps of: forming a thermoplastic bonding layer on a back side of the flat display device; mounting a connector for connecting a driver circuit to the electrode on a flexible printed board, and forming a wiring for connecting the connector to the electrode on a flexible printed board; forming a bump on a portion corresponding to the wiring in the flexible printed board; heating the bonding layer, and bonding the flexible printed board onto the back side of the flat display device with pressure in a state of contacting the bump with the electrode; covering the back side of the flat display device with a sealing member having an opening at its part thereof so that the connector is passed through the opening; and sealing a contact portion of the connector with the sealing member.
Further, the present invention provides a wiring method for connecting an electrode to a driver circuit in a flat display device laminating a display material and an electrode, comprising the following steps of: forming an insulative protection layer on a back side of the flat display device; mounting a driver circuit and a connector for connecting a signal line and power supply line to the driver circuit on the protection layer, and forming a wiring for connecting the connector to the electrode and a wiring for connecting the connector to the driver circuit on the protection layer; covering the back side of the flat display device with a sealing member having an opening at its part thereof so that the connector is passed through the opening; and sealing a contact portion of the connector with the sealing member.
Further, the present invention provides a wiring method for connecting an electrode to a driver circuit in a flat display device laminating a display material and an electrode, comprising the following steps of: forming a thermoplastic bonding layer on a back side of the flat display device; mounting a driver circuit and a connector for connecting a signal line and power supply line to the driver circuit on a flexible printed board, and forming a wiring for connecting the driver circuit to the electrode and a wiring for connecting the connector to the driver circuit on the flexible printed board; forming a bump on a portion corresponding to the wiring for connecting the driver circuit to the electrode in the flexible printed board; heating the bonding layer, and bonding the flexible printed board onto the back side of the flat display device with pressure in a state of contacting the bump with the electrode; covering the back side of the flat display device with a sealing member having an opening at its part thereof so that the connector is passed through the opening; and sealing a contact portion of the connector with the sealing member.
Further, the present invention provides an image display system having a plurality of display panels which are arranged in an adjacent state so as to constitute a single screen, wherein the display panel comprises a flat display device laminating a display material and an electrode, and a wiring for connecting a driver circuit to the electrode is led from an inside of a sealing member covering a back side of the flat display device to the back side of the flat display device.
Further, the present invention provides an image display system having a plurality of display panels which are arranged in an adjacent state so as to constitute a single screen, wherein the display panel comprises a flat display device laminating a display material and an electrode, and a driver circuit connected to the electrode is arranged inside a sealing member covering a back side of the flat display device, and further, a wiring for connecting a power supply circuit and a signal supply circuit to the driver circuit to the electrode is led from an inside of a sealing member to the back side of the flat display device.